The present invention relates to optical analysis systems and methods for analyzing chemical compositions and, in particular, to portable handheld characteristic analyzers used to analyze chemical compositions in or near real-time.
In the oil and gas industry, it can be important to precisely know the characteristics and chemical compositions of fluids and substances found in and about oil refineries or other hydrocarbon processing facilities. For example, there is an ever-increasing emphasis in reducing or otherwise preventing gaseous emissions and leaks from refineries and other processing facilities, given the environmental and health threats such emissions may pose. Knowing which chemical compositions are being emitted/leaked and the location and concentration of such emissions/leaks can prove advantageous in remedial efforts to reverse or stop the undesirable effects.
Detection and identification of chemical compositions include, inter alia, the use of surface acoustic wave detectors, ion mobility spectrometers, flame photometric detectors, and the like. In surface acoustic wave detectors, the target chemicals are absorbed or adsorbed onto a specific coating of a piezoelectric substrate, to thereby vary its mass. The mass change affects the resonance frequency of the piezoelectric substrate which is measured using an appropriate electronic circuitry. In ion mobility spectrometers, a gaseous sample is ionized in an ionization region within the spectrometer, e.g., using a radioactive source, and accelerated over a short distance to a detector. The gaseous sample is analyzed by measuring a characteristic time-of-flight of the negative and positive ions from the ionization region to the detector. In flame photometric detectors (FPDs) a gaseous sample is introduced to a hydrogen rich flame and electrons in the outer shell of atoms obtained from the target chemicals are excited to higher energy states. When an excited electron returns to its ground state, energy is emitted in the form of light by which the presence of target chemicals is confirmed. The wavelength of the emitted light depends on the target chemical, whereas its intensity depends on the chemical's concentration.
Portable detectors based on the above techniques are generally known. However, the above-noted techniques have limited sensitivity and selectivity in particular environments, such as industrial environments in which the detection and identification of chemical compositions are often performed under less than optimal conditions. Consequently, more accurate determinations of chemical compositions are usually conducted off-line using retrospective laboratory analyses, such as spectroscopic and/or wet chemical methods, which analyze an extracted sample of the chemical composition. Although off-line, retrospective analyses can be satisfactory in certain cases, they nonetheless do not allow real-time or near real-time analysis capabilities to be realized but instead often require hours to days to complete the analysis. During the lag time between collection and analysis, the characteristics of the extracted sample of the chemical composition oftentimes changes, thereby making the properties of the sample non-indicative of the true chemical composition or characteristic.
Reliable onsite, real-time detection of chemical compositions is of utmost importance in order to monitor how detected chemical compositions change over time, thereby serving as a quality control measure for processes in which fluids and other substances are used.